Recently, terminals with novel functions are developed rapidly, and as the distribution of the terminals are expanded, the terminals capture a gradually increasing share of people's lives.
In addition, a terminal, such as a smart phone, that is popularized with the development of the mobile communication technology uses various keys that are used by being provided on the rear face and the side face of the terminal as well as being provided on the front face of the terminal.
Further, as users' needs for terminals are gradually diversified, a key used in such terminals includes a waterproof structure in order to prevent a fluid from infiltrating into the terminals.